US firm Willkie Farr & Gallagher has been sued for overbilling by the city of San Diego's chief prosecutor.
City attorney Mike Aguirre filed a claim last week for $29.2m (£14.3m) against New York-headquartered Willkie, which the city employed in an 18-month-long securities fraud probe alongside risk management consultancy Kroll.
The project ended up costing the city $20m (£9.93m), and the amount for which Aguirre is seeking redress is triple the amount billed by Willkie.
Aguirre, who filed two motions without the approval of San Diego's council, alleges that Willkie duplicated the work of Kroll and went beyond its contract by billing for items such as lobbying work.
The two motions, one on behalf of Californian residents and the other on behalf of San Diego, could yet be consolidated.
A Willkie spokesperson was unavailable for comment.